research findings

Fragmented & Young Forest preferred by Migrating Songbirds

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Black-throated Green Warbler
Creative Commons License photo credit: Jim Frazier

Research published in Vol. 126, Iss. 3, pg. 579 of The Auk has some interesting implications for habitat conservation for migrating bird species here in eastern North America. In short, during Spring and Fall migration, migrants showed no preference for stopover locations based on distance from a continuous, connected (river corridor) habitat, nor were they more likely to be concentrated in one forest patch over another. Plainly, the migrating birds appear to show no preference for connected habitats versus fragmented ones. Clearly, if this is the case, birds are using other criteria to select where they stop while migrating.

What is interesting, and not surprising, is the finding that during Fall migration, birds do select habitat described as “early succession forest” with high density of native and non-native fruit-bearing trees and shrubs. In the cannon of conservation, habitats that are fragmented or in the early stages of succession are seen as lower quality when compared to continuous and stable habitats. And this may still be the case when it comes to nesting (less nest predation in larger forests, for example)—but it would seem as though we might need to re-evaluate the assumption that these younger, more fragmented landscapes are of little or no use to birds and ultimately, bird conservation.

As migratory stopovers, it would seem that all forested landscapes—no matter how mature—are important.

Female Blue Tits use home-made potpourri in nests to to attract males and have healthier chicks

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Blue Tit by Marko_KBlue Tit used under a creative commons lisence by Marko_K. Thanks Marko!

Blue Tits (Cyanistes caeruleus) nesting on the Medeteranian island of Corsica have been known to incorporate fresh sprigs of aromatic plants, like French Lavender (Lavandula stoechas) into their nest cups. New research1 reports that there may be benefits beyond a nest that smells like potpourri: these aromatic plants offer benefits to larger broods of Blue Tit chicks.

The potpourri, interestingly, does not reduce the number of ectoparasites2 found on the birds in the nest. Rather, the researchers suggest that either the aromatic plants offer immune system benefits (mechanism still unknown) or, and I quite rather like this idea, the females that actively incorporate fresh sprigs of aromatic plants are indicating their fitness to males. In other words, the fresher, more aromatic the nests, the “better” the female is as a mate (and subsequently, the “better” the offspring).

Now that makes you think about that stale bowl of potpourri on the back of your great-aunt’s toilet tank differently…

  1. Aromatic plants in nests of blue tits: positive effects on nestlings by Adèle Mennerata, Philippe Perreta, Patrice Bourgaultc, Jacques Blondela, Olivier Gimeneza, Don W. Thomasc, Philipp Heebb and Marcel M. Lambrechtsa [↩]
  2. Corsican Blue Tits hold the distinction of having the highest known “loads” of blow fly larvae, for example [↩]